FLOWERS INTO SHOOTS - PHOTO AND HORMONAL-CONTROL OF A MERISTEM IDENTITY SWITCH IN ARABIDOPSIS

Little is known about the signals that govern the network of meristem and organ identity genes that control flower development. In Arabidops is, we can induce a heterochronic switch from flower to shoot developm ent, a process known as floral meristem reversion, by manipulating pho toperiod in the floral homeotic mutant agamous and in plants heterozyg ous for the meristem identity gene leafy. The transformation from flow er to shoot meristem is suppressed by hy1, a mutation blocking phytoch rome activity, by spindly, a mutation that activates basal gibberellin signal transduction in a hormone independent manner, or by the exogen ous application of gibberellins. We propose that LFY and AG play an im portant role in the maintenance of flower meristem identity and that f loral meristem reversion in heterozygous lfy and in ag flowers is regu lated by a phytochrome and gibberellin signal transduction cascade.